Why does Jesus' "suffering" matter?

[Nope]

you are making a huge assumption.  Jesus did not die on a cross, jesus was not buried in a tomb and he did not come back to life

Then why do Roman and Jewish historians say that He died on a cross?

. Every time that I have read the documents that Christians claim prove Jesus existed, it turns out that the document writers were simply describing what Christians believe. No one is disputing that Christians existed so the documents prove nothing. If I write down what Muslims believe that doesn't also mean that I believe in their mythology